Fuel calorimeter and process



Dec. 31, 1935. R. w. KEITH FUEL CALORIMETER AND PROCESS Original FiledAug. 26, 1930 2 Sheets-Sheet 1 INVENTOR fag! z/l u ATTORNEY WTNESSESDec. 3l, 1935. R. w. KEITH FUEL CALORIMETER AND PROCESS original Filed'Aug. 2e, 1930 2 sheets-sheet 2 INVENTOR OQ OO www @N ATTORNEY PatentedDec. 31, 1935 UNITED STATES PATENT OFFICE Application August 26, 1930,Serial No. 477,888 Renewed November 28, 1933 16 Claims.

This invention relates to an improved fuel calorimeter, and has for itsobject to provide an improved instrument to determine the heating Valueof fuels, particularly liquids or gaseous fuels. y

Another object of the present invention is to provide an instrumentwhich is accurate and in which the accuracy can be easily checked.

An additional object of the invention is to provide an instrument whoseindication is dependent only on the heat value of the fuel.

A further additional object is to provide an instrument whose indicationis unaffected by ordinarychanges in atmospheric conditions, such 4 aschanges in temperature, pressure and relative humidity. A still furtheradditional object of the invention is to pro-vide an instrument whichwill be fully automatic and which will present either a visualindication or a record on a moving strip of paper or other article.

In the accompanying drawings- Figure 1 is a longitudinal Verticalsectional View through the principal part of a fuel calorimeterembodying the invention;

Figure 2 is a diagram illustrating the operation metal or other heatresisting material of some kind. The structure shown in Figure l isintended to circulate air and gas in a manner hereinafter described andto utilize a known energy for producing heat and utilizes gas or liquidfuel having an unknown heat value. As indicated by the arrows, air atatmospheric temperature is permitted to enter the passageway 3 andeventually exhaust out through the passageway 4. When the device is infull operation the air will usually automatically circulate, but instarting the de- Vice, and sometimes in operating it, it may benecessary to use a fan to force air into the passageway 3 under a givenpressure, which is preferably very slight and only suiiicient to causeair to ow substantially evenly throughout the device.

Air entering passageway 3 will pass through the heat exchange chamber 5and into the pri.- mary air entrance section or passageway 6. The heatexchange chamber 5 is provided with a number of tubular members Ipreferably of metal and extending entirely through chamber 5 so as toreceive the air and products of-cornbustion from chamber 8 and dischargethe same into chamber 9. In this way the gaseous matter passing throughthe tubes I will become cooled while at the same time air passing intothe passageway 6 will be warmed. Preferably the device is so designedthat the air or gaseous matter in passageway 6 will be of substantiallythe same temperature as the air or gaseous m'atter in the secondary airentrance section or passageway 9, or at least it will be ofsubstantially the same temperature at the respective entranceresistances I il and II. The air in the passageway 6 will move past theburner I 2 into the passageway I3 and be heated by the heatl produced bythe burner I2.

A number of foraminous plates I4 are arranged in the passageway I 3, theholes in the various plates being staggered so as to prevent radiantheat reaching the resistance I5, and also to cause the gases to mix asmuch as possible. From theV chamber 8 the gaseous matter flows throughpipes 'I into the secondary entrance section 9 and slightly heatsresistance II. The air and gases passing from resistance II willencounter the heating element I6 arranged in the secondary heatingchamber I1. This heating element may be of any preferred kind fordissipating heat at a known rate and transmitting a known amount oi heatto the flowing gases. Electricity is a form of energy that can bereadily measured, and as electricity can be easily transformed intoheat, an electric heater has been shown as a desirable heating element.As the gaseous matter passes the heater I 6 it will be heated but thefo-raminous bailies I8 will prevent radiant heat reaching resistance I 9while allowing the heated gases to freely pass.

The bailies I4 and I 3 are intended to prevent any direct heat from therespective burners or heaters reaching resistances I5 and I9 so that theresistances I5 and I9 will be only affected by the temperature of thegas.

As the air passes through the heat exchange chamber 5 it isheated, andas the air and gases (products of combustion) pass through the tubes 1they are cooled so that air or gaseous matter striking the resistancesI0 or I I will heat the same to substantially the same temperature. Itwill be evident that in the heat exchange chamber the tubes TI andassociated parts may be proportioned so that this result will be securedwith reasonable accuracy. This arrangement is provided in order to makethe average temperature of II and I9 equal, or nearly equal to theaverage temperature of I0 and I5 when the difference in temperaturebetween II and I9 is equal to the difference in temperature between I0and I5.

It will be noted that in order that the heat supplied by the heatingelement I6 in unit time be the same as the heat supplied by burner I2 inunit time, the difference in temperature between resistances I0 and I5must be equal to the difference in temperature between resistances I Iand I9. Also the same weight of gaseous matter must pass chambers I3 andIl in unit time and the average temperature between I0 and I5 must benearly equal to the average temperature between II and I9.

In order to more specifically set forth the operation of the instrumenta specific example is given below, but it will be understood that thisis only one example in order to show the functioning of the device, andthe device is, of course, not limited in any way to the temperature setforth.

For the present example itis to be assumed that the air entering at 3 isat 70 F. and going through chamber 5 the entering air is heated to, say,F. so that the resistance I0 is at 120 F. In chamber I3 combustion takesplace by reason of the action of burner E2 and the air and products ofcombustion are heated, for instance, to 175 F. so that the resistance I5is at a temperature of 175 F. The difference of temperature produced bythe burning fuel is then the difference between the temperature ofresistance I5 and the temperature of resistance I0, namely, 175 minus120=55 F. From the primary heating chamber 0 the air and products ofcombustion go through the inside of the tubes l of the heat exchangedevice whereby they are cooled to, say, F. As the` air and products ofcombustion pass resistance I I at this temperature it naturally causesthe temperature of resistance II to be of 125 F. This temperature isnearly equal to the temperature of resistance I0.' The temperature ofresistances I0 and II can be identical, or they can be slightlydiiferent as just mentioned, or they can be widely different, althoughpreferably they are near the same, as just mentioned. After the air andproducts of combustion pass resistance II they go through chamber I1where the secondary source of heat I5 is located. If the electric heateror secondary source of heat i5 heats the air and products of combustionto 180 F. then the increase in temperature produced by the heater I6 is180 minus 125=55 F. which is the same as the difference in temperatureproduced by the burning fuel.

Therefore the average temperature between resistance i5 and resistanceI0 is 147.5" F. or 1/2 plus 120 F.) This is very nearly the same as theaverage temperature between resistance I9 and resistance II, namely,152.5 F. or 1/2 (180 plus 125 FJ. It will thus be noted that the averagespecific heat of the air and products of combustion flowing through theprimary heating chamber is (with negligible error) numerically equal tothe average specific heat of the air and products of combustion flowingthrough the secondary heating chambers.

The same weight of gases circulates in a given time through chambers I3and I'I and their average specific heats are substantially the same,

resistance I5 and resistance I0.

and the rise of temperature produced by the burning fuel in chamber E3is numerically equal to the rise in temperature produced by the heaterI6, consequently the heat added to the flowing gases by the burning fuelis nurnerically equal to 5 the heat added to the flowing gases by theheater during the same time interval. Knowing the rate at which fuel isbeing supplied to the burner and the rate at which electrical energy issupplied to the heater, the heating value of the fuel 10 can be readilycomputed. For example: If during the run the current used by the heaterI6 has a heat equivalent of 1000 B. t. u. and if for the same time onepound of fuel has been used in the burner i2 it will be evident that thefuel has a 15 heating value cf 1000 B. t. u. per pound.

When it is desired to use the instrument in practical work the burner islighted and then the power input to the heating element I6 is adjusteduntil the difference in temperature be- 20 tween the resistances I0 andII is numerically equal to the difference in temperature between Whenthis occurs the bridge illustrated in Figure 2 becomes balanced and thegalvanometer needle swings 25 to zero, It will, therefore, be seen thatthe bridge determines the point when these two differences intemperature are equal, regardless of the actual numerical magnitude ofthese differences. 30

In order to secure an accurate reading the operator should know when thetemperature differences i5-I0=IQ-II. 1n order to visually disclose thisthe resistances are connected up as two legs of a Wheatstone bridge, asshown in 35 Figure 2.

With regard to the various resistances I0, II,

I5 and I0 it is to be noted that they are preferably in the form ofcoils and are made of resisting material whose resistance varies propor-40 tionately to the absolute temperature. A good material for this usewould be platinum, although other materials either alone or incombination may be used without departing from the spirit of theinvention. When made of this material 45 it can be seen that the fourresistances I0, I5, II, I9, are formed so that when all are at the sametemperature their values as electric resistances are equal. The othertwo legs of the bridge are constituted by resistances 20 and 2| which 50are respectively equal and which are preferably nearly equal inresistance to the other two legs of the bridge, although not necessarilyso. Also, the resistances 20 and ZI should be kept at the sametemperature and under the same condi- 55 tions, and in order to do thisthey may be wound on the same spool or kept in the same bath of oil sothat the electric resistance of 20 is equal tc the electric resistanceof 2|. It will also be evident that when the calorimeter is not in 60operation and the resistances I0, I5, II and I9 are at the sametemperature, the bridge will be balanced. This balance constitutes acheck on the proper operation of the instrument. It will also be notedthat when the temperature of re- 65 sistance I5 minus the temperature ofresistance i0 is equal to the temperature of resistance I9 minus thetemperature of resistance II, the bridge is balanced because the valueof the electrical resistance of resistances I5, I5, II and I9 varydirectly with absolute temperature.

-From the foregoing it will be readily seen that if the difference intemperature produced by the burning fuel is different from the rise oftemperature produced by the secondary source 75 of heat, namely, theheater I6, the bridge will be thrown out of balance and the galvanometer22 will swing one way or the other depending on which of the twodifferences is larger. It will be noted that asuitable source of power23 must be provided for the bridge, as shown in Figure 2, said powerbeing connected to the points 24 and 25 respectively. This current is,of course, small whereas the current to the heater I6 varies accordingto the heating needed.

In Figure 3 will be seen a diagram wherein the apparatus illustrated inFigure 1 is connected to automatic means whereby current is increased ordecreased automatically in the heater until the difference intemperature between resistances I9 and I I is equal to the difference intemperature between resistances I5 and I0. Referring to the diagram itwill be noted that bridge 26 is the same as the bridge shown in Figure2, but instead of having a galvanometer 22 wires 21 and 28 lead frompoints 29 and 39 to the windings of a polarized relay. This relaycontrols the magnetically operated switch 32, which switch is adapted tocontrol the current supplied to the motor 33. It will be noted thatswitch 32 is supplied with current from the wires 34 and 35, which wiresreceive their current from the lbus wires 36 and 37. Bus wire 36 extendsto the contact arms 38 and 38 of the rheostat 39, while bus wire 37extends to one terminal of the recording wattmeter 4G, the oppositeterminal of wattrneter 4i] being connected through wire 4I to thecontact post 42 of rheostat 39.

The arm 38 of the rheostat 39 is rigidly secured to a worm wheel 43meshing continually withthe worm 44. Worm 44 is secured rigidly to thearmature of motor 33 whereby whenever this motor operates arm 38 will beswung. When the polarized relay 3I has been moved to one position arm 39will move in one direction, and when the polarized relay is moved to theother position arm 38 will move in the opposite direction, whereby moreor less current is turned on to the heater I6 according to thecircumstances. It will also be noted that when the bridge is balancedthe relay is in neutral position and the motor stops.

In the case of automatic operation the fuel is supplied to the burner I2at a known and constant rate by means of a suitable device, as, forinstance, a positive displacement pump kept at a constant temperatureand driven at a constant speed. As the power input to the electricheater IE is automatically adjusted until the temperature differencebetween resistances I9 and II is numerically equal to the temperaturedifference between resistances I5 and Il), then the reading of thewattmeter is a measure of the heating value of the fuel being tested. Itis to be understood that the wattmeter scale can be calibrated to readheating value in any unit desired.

In Figure 4 a slightly modied form of that shown in Figure 3 has beendisclosed. In this form the rheostat 39 and associated parts areidentical with that shown in Figure 3, with the exception that arm 38 isprovided with an extension 45 adapted to receive a stylus 46. Atraveling strip of paper or other material 47 is arranged in the path ofthe stylus 45 and is adapted to be marked thereby. In this way a recordmay be made 4continually and automatically. When power is supplied towires 31 and 36 at a constant potential, it is evident that the rheo- 1stat can be calibrated so that a certain displacement represents a givenpower input to the electric heating element of the calorimeter. 'I'hepen or stylus 46 on the arm 48 records directly on the paper or othermoving element 41. In this way the recording wattmeter is not necessary.5 When operating the device, it is cause to function for someappreciable time before a test is taken in order that the action will beas uniform as possible. In operation, there may be some slight errors,but these are negligible and do not 10 aiTect the reasonable accuracy ofthe device. For instance, the fuel supplied to the burner is at a lowertemperature than the resistance I 0 and, consequently, a certain amountof heat is to be expended for warming the incoming fuel to the 15ytemperature of resistance I6. This fact produces a small error but thiserror is negligible in most cases. However, this error may be entirelyeliminated by preheating the incoming fuel to the temperature ofresistance I9, but, as just stated, 20

the error is so negligible that it does not materially affect the nalresult.

When bringing the instrument to a thermal balance a small lag existsbetween the time that you change the adjustment of the heating ele- 251,

ment and the time that resistance I9 gets heated up to the temperatureof the owing gas but this lag on starting has nothing to do with theaccuracy obtained when the device is functioning properly. and productsof combustion are flowing at a steady rate, the weight flowing past theportion I3 is in a given time numerically equal tothe weightsrespectively flowing past I4, I5, 9, II, IE, I8 and I 9. Now, if a givenportion A passes 35 between I0 and I5 and affects those resistances, itis not necessary to wait until the same portion A goes through the heatexchanger and nally comes to II and I9 because at the very same instantthat the given portion A went 4'0 past I3 and I5, another portion B ofexactly the same Weight went past Il and I9.

What I claim is:

1. The method of determining the heat value of a fuel having an unknownheat value, which 45..

consists in burning the fuel in the presence of preheated air to produceheated gases, cooling said gases to substantially the originaltemperature of the preheated air, subjecting said cooled gases to heatfrom a second source, varying the 50 heat from said second source untilthe rise of temperature of the gases at its second heating issubstantially the same as the rise of temperature given to the heatedgases by burning of the fuel, and then measuring the energy used inproducing the heat of the second mentioned source.

2. The method of determining the heat value of a fuel, which consists inburning the fuel in the presence of air to produce heated gases, coolingsaid gases, subjecting said cooled gases to the heat from a secondsource, measuring the fuel applied to the burner in unit time, varyingthe energy supplied in said unit time to said second source by measuredquantities, and then determining when the rise in temperature of the airproduced by the fuel is equal to the rise' in temperature of the gasesproduced by the second heat source.

3. A fuel calorimeter including means forming a continuous passagewayfrom one point to ansistance arranged near each of said outlets, a, 754

It wiil be noted that since the air 30v burner using fuel of unknownheat value arranged in said passageway adjacent one of said outletswhereby the gaseous matter passing the burner will have the temperaturethereof in- 5,V creased, a resistance arranged adjacent said burner andpositioned to have its temperature increased by said heated gaseousmatter, said heated gaseous matter passing through said heat eX- changeapparatus to the other of the first menlci tioned resistances, a secondsource of heat for heating said gaseous matter a second time, a fourthresistance adapted to thereafter be heated by said heated gaseousmatter, means for regulating the heat of said second source of heat, 15,means for measuring the fuel supplied to said burner in a unit time, andmeans for measuring the energy used in said unit time by said secondsource of heat.

4. A fuel calorimeter including a heat exchange 2m apparatus having- `anair passageway therethrough, means for directing air into s-aidpassageway, a burner supplied with fuel of an unknown heat value, meansfor cirecting air from said passageway past said burner, means for di-25' recting the products of combustion from said burner through saidheat exchange device, a heating member dissipating heat at a known rate,means for directing said products of combustion after passing throughsaid heat exchange 30v device to said heating member for re-heating saidproducts of combustion, a pair of resistances arranged near said burner,the respective resistances being on opposite sides of the burner, a pairof identical resistances arranged near said 35i-,heating member, therespective resistances of said last mentioned pair being on the oppositesides of said heating member so that the temperature of one resistanceof each pair will be raised respectively by the heated air and products401101ek combustion, said pairs of resistances being identical, meansfor varying the heat from the member dissipating heat at a known rate,means for measuring the amount of fuel supplied in unit time to theburner, means for measuring the 45: energy used in unit time by theheating member dissipating the heat at a known rate, and meansassociated with both pairs of resistances forming a Wheatstone bridgefor indicating when the differences in temperature between the membersof 50? the respective pairs of resistances are equal.

Y 5. A calorimeter co-mprising a housing formed with a passagewaytherethrough having an air inlet and an air outlet, said passagewaybeing formed into a primary heating section, a second- 55v ary heatingsection, a primary air inlet section discharging into said primaryheating section, a secondary air inlet section discharging into saidsecondary heating section, and a heat exchange section having tubularmeans connecting the out- 601` let of said primary heating section withthe inlet of said secondary air inlet section, a burner at the inlet ofsaid primary heating section, said burner being adapted to use acombustible of unknown heat value, a foraminous baiiie arranged 65 insaid passageway immediately above said burner, a resistance positionedin said primary heating section on the opposite side of said bai-He tosaid burner whereby its temperature will be raised by the flow of heatedgases through said 70 primary heating chamber, identically formedresistances arranged respectively substantially centrally of saidprimary air inlet section, and said secondary air inlet section, anelectric heater. positionedin the entrance of said second- 75'; ary.heating section,.aforaminous bale arranged the temperature differencebetween the resistances in said primary heating section is equal to thetemperature .diference between the resistances in said secondary heatingsection.

6. A calorimeter comprising a primary and a second-ary heating chamber,a pair of identical V resistance elements in each of said chambers, aheat exchanger positioned to heat and direct the heated air into saidprimary heating chamber and to receive the products of combustion fromsaid heating chamber, cool the same and direct the coole-d products ofcombustion to the secondary heating chamber, said heat exchanger causingthe air entering the primary heating chamber and the products ofcombustion leaving the secondary heating chamber to be at approximatelythe same temperature, a heater formed as a burner for said primaryheating chamber, said burner being adapted to use a combustible of anunknown heat value, a heater for said secondary heating chamber, saidsecond mentioned heater dissipating heat at a known rate, means forvarying the heat from said seco-nd mentioned heater, means for measuringthe fuel supplied to said burner in unit time, means for measuring theenergy supplied to s-aid second mentioned heater in said unit time, saidresistances in each chamber being respectively at opposite sides of therespective heaters and means for indicating when the temperaturedifferences between said pairs of resistances are equal.

7. A calorimeter including primary and secondary heating chambers, apair of identical resistance elements associated with each of saidchambers, a heat exchanger positioned to heat and direct air into saidprimary heating chamber and to receive the products of combustion fromsaid primary heating chamber, cool the products of combustion and directthe cooled products of combustion into said secondary heating chamber,said heat exchanger acting on the air and products of combustion so thatthe air entering the primary heating chamber will be at substantiallythe same temperature as the products of combustion entering thesecondary heating chamber,

a burner for said primary heating chamber for heating the air suppliedthereto, said burner being adapted to use a combustible of unknown heatvalue, a heater for said secondary heating charnb-`^ for heating theproducts of combustion supplied thereto, said heater dissipating heatenorgy at a known rate, means for varying the supply of energy to saidheater to vary the temperature in the secondary heating chamber, theresistances in the primary chamber being on opposite sides of saidburner and the resistances in the secondary chamber being on oppositesides of said heater and means for determining when the diierence intemperature between the resistances in said primary heating chamber isequal to the difference in temperature between the resistances in saidsecondary heating chamber.

8. A calorimeter including primary and secondary heating chambers, aheat exchanger positioned to heat the air entering said primary heatingchamber and cool the gases leaving the pri- Cil mary heating chamber,said heat exchanger directing said gases into said secondary heatingchamber, said heat exchanger causing the air entering the primaryheating chamber to be at substantially the same temperature as the gasesentering the secondary heating chamber, an entrance resistance elementpositioned at the entrance to each of said heating chambers, saidelements being identical and positioned to have their temperaturesvaried by the air or other gases entering said chambers, identicalresistances positioned in each of said heating chambers, a burneradapted to use a combustible of unknown heat value positioned to heatthe air as it passes through the primary heating chamber, a heater usingenergy at a known rate positioned to heat the gases passing through saidsecondary heating chamber, means for varying the energy supplied to saidheater, said resistances in said heating chamber, said entranceresistances and two auxiliary resistances being connected to form abalanced electric circuit responsive to changes in the rise oftemperature of the gases flowing through either the primary or secondaryheating chambers, means for registering the rate of supply of energy tosaid heater so that when the burner is supplied with fuel at a known andconstant rate, the record of the power supply to the heater is a measureof the heating value of the fuel being consumed in the burner at thetime of registering.

9. A calorimeter including a primary heating chamber provided with aprimary air entrance section, a secondary heating chamber provided Vwitha products of combustion entrance section,

a heat exchanger positioned to heat the air entering said primary airentrance section and cool the products of combustion iiowing from saidprimary heating chamber to said products of combustion entrance chamber,said heat exchanger causing the air entering the air entrance sectionand the products of combustion entering the products of combustionentrance section to be of substantially the same temperature, identicalresistance coils in each of said sections, identical resistance coilspositioned in each of said chambers, a burner adapted to useacombustible of unknown heat value, said burner being posi-A tioned todirect all of its heat into said primary chamber, whereby thetemperature of the air and resistance in the primary chamber will beraised, a heater dissipating heat at a known rate positioned so that allthe heat therefrom will be directed into secondary heating chamber forraising the temperature of the air and products of combustion andresistance therein, means for connecting the resistance coil in saidprimary heating chamber in series with the resistance coil in saidprimary entrance section, means for connecting in series the other tworesistance coils, and means including an electric circuit for balancingthe resistance of one pair of said resistance coils against the other todetermine when the temperature dilerences between the respective pairsof coils are equal.

10. A calorimeter including a primary heating chamber provided with anair entrance section, a secondary heating chamber provided with an airand products of combustion entrance section, a heat exchanger positionedto heat and direct air into said primary air entrance section andreceive air and products of combustion from said primary heatingchamber, cool the same and then direct the same into said air andproducts of combustion entrance section, said heat exchanger causing theair entering said primary air entrance section and the air and productsof combustion entering the air and products of combustion entrancesection to be at substantially the same temperature, a resistance coilarranged 5 in each of said sections, said coils being identical, aresistance coil positioned in each of said chambers, said coils beingidentical, a burner using a fuel having an unknown heat value positionedto heat the air passing through said primary heating chamber, a heaterusing an energy at a known rate positioned to heat the air and productsof combustion passing through the secondary heating chamber, means forconnecting in series the coils in said primary entrance section and saidprimary heating chamber, means for connecting the other two coils inseries, means forming a balanced circuit with each pair of coils actingas a leg of said circuit, and means controlled by a difference inresistance 'of said 20 pairs of coils for regulating the energy suppliedto said heater.

11. A calorimeter including a primary heating chamber provided with anair entrance section, a secondary heating chamber provided with aproducts of combustion entrance section, means connecting said airentrance section to said products of combustion entrance section, saidmeans including a heat exchanger positioned to heat and direct air intosaid air entrance section and receive products of combustion from saidprimary heating chamber, cool the same, and direct the cooled productsof combustion into said secondary heating chamber, said heat eX- changeracting to cause the air to enter said air entrance section atsubstantially the same temperature that the products of combustion enterthe products of combustion entrance section, a resistance' coil arrangedin each of said sections,

I said coils being identical, a resistance coil ar- 40 ranged in each ofsaid chambers, said last mentioned coils being identical, a burner usinga fuel of unknown heat value for heating the air in said primary heatingchamber, whereby the coil in said primary heating chamber will have itstemperature raised, a heater using an energy at a known rate positionedto heat the products of combustion in said secondary heating chamberwhereby the temperature of the resistance coil in said secondary heatingchamber will be raised, means for connecting said resistances in pairsso that the resistance coil of the primary heating chamber will be inseries with the resistance coil in the air entrance section, and theother resistance coils will be in series, means for forming a balancedcircuit of the Wheatstone bridge type, said means using the respectivepairs of coils as two legs of the bridge, means for supplying current tosaid balanced circuit, a polarized relay connected to the center of saidbalanced circuit whereby when said balanced` circuit is out of balancesaid polarized relay will be moved accordingly, and means controlled bysaid polarized relay for supplying more or less energy to said heateraccording to the direction 55 in which said polarized relay has beenmoved.

12. A calorimeter including a primary heating chamber provided with aprimary air entrance section, a secondary heating chamber provided witha products of combustion entrance section, a heat exchanger positionedto heat and direct the heated air into said primary air entrance sectionand to receive the products of combustion from said primary heatingchamber, cool the same and direct the cooled products of comtrancesection at substantially the same temperature as the air entering saidair entrance section, an entrance resistance coil positioned in each ofsaid sections, said entrance resistance coils being identical, a testingresistance coil positioned in each of said chambers, said testingresistance coils being identical, a burner for using combustible ofunknown heat value, said burner -being positioned tol direct all of itsheat into said primary chamber whereby the temperature of the `coiltherein will be raised, an electric heater for heating the air andproducts of combustion in said secondary heating chamber, a rheostatmeans including an arm for controlling the current supplied to saidelectric heater, means for .recording and indicating the current used insaid said rheostat for moving the arm thereof back and forth accordingto the way in which said polarized relay acts, whereby more or lesscurrent is supplied to `said electric heater.

v13.. A calorimeter including a balanced circuit of the Wheatstonebridge type, the circuit having two legs formed with identicalresistances, each leg comprising primary and auxiliary resistances inseries, a primary heating chamber surrounding one of the primaryresistances, an auxiliary heating chamber surrounding the other primaryresistance, a heat exchanger positioned to heat air and direct theheated air into contact with one of said auxiliary resistances forheating the same, said heated air passing into said vprimary heatingchamber, said heat exchanger being also in a position to receive, cool,and direct the products of combustion from said primary heating chamberinto contact with the other of said auxiliary resistances for heatingthe same, said products of combustion lowing from said other auxiliaryresistance tosaid auxiliary heating chamber, said heat exchanger actingto cause .the air entering the primary heating chamber to be atsubstantially the same temperature as the products of combustionentering the auxiliary heating chamber, a burner using a fuel of unknownheat value for heating the air entering -said primary heating chamber,the products of 'combustion from said burner acting to heat the Yprimaryresistance in one of said legs, a heater dissipating heat at a knownrate for heating the Yproducts of combustion in said auxiliary chamber,-said heated products of combustion heating the other primaryresistance, and means for Varying the heat produced by said heater.

14. A calorimeter including means forming a heat exchange apparatushaving a passageway for cool air and a passageway for heated air,

ibustion into said products of combustion enmeans for directing cool airthrough the rst passageway, tubular means for directing said air afterit has passed through the first passageway to the second passageway,tubular means for directing said air after it has passed through thesecond 5 passageway to a discharge point, a heater using fuel of anunknown heat value positioned to heat the air as it passes through thefirst tubular means, a heater having a known heat Value which may beregulated, said last mentioned heat- 10 er being positioned to neat saidair as it passes through the second tubular means, a primary resistancepositioned in the outlet end of said first passageway, a` second primaryresistance positioned in the outlet end of said second passageway, saidresistances being identical, a secondary resistance positioned in theiirst tubular means between the rst mentioned heater and said secondpassageway, an auxiliary secondary resistance positioned in the secondtubular means be- 20 tween the second mentioned heater and saiddischarge point, said secondary resistances being identical, means forVarying the heat from the heater dissipating heat at a known rate, meanscomprising an electric circuit including all of said 25 resistances andforming a Wheatstone bridge with the primary resistance in the outlet ofthe rst passageway and the secondary resistance in the iirst tubularmeans in one leg of the bridge and the other two resistances in theother leg of the 3o bridge .for indicating when the difference intemperature is equal.

15. The method for continuously determining the heating value of acombustible comprising the burning of the combustible at a denite volu-35 metric rate in a stream of gaseous working fluid, measuring the riseof temperature in the working iiuid due to said burning, thereafterheating the same iluid stream by a supplementary measurable heatingsource at a measured rate of heat 40 input that is kept substantiallyequalized with respect to the aforesaid temperature rise, said stepsbeing performed in successive stages of which the initial temperaturerise of the iirst stage is substantially equal to the nal tempera- 45ture rise in the other stage, the heat input of the second stage beingemployed as an index of the caloric value of the combustible of the rststage.

16. The method for 4continuously determining 50 the heating value of acombustible and which method consists in the following successive steps,Viz: firstly, providing for a gaseous Working uid containing anoxidizing agent and establishing a iiow of such fluid; secondly, burningthe combus- 55 tible at a predetermined rate to initiate a measurabletemperature rise in a localized portion of such fluid stream; thirdly,cooling said stream portion to substantially reestablish its originaltemperature; and thereupon subjecting the cooled stream 50 portion to ameasured independent heat source until the temperature rise therebyimparted shall maintain said stream portion in a thermally balancedrelation with respect to the aforesaid initiated temperature rise.

RAFAEL WILLIAM KEITH.

